Discrete Multitone ADSL
Consists of up to 255 4.3125 KHz channels, each containing a QAM modem (each QAM modem has a 4 KHz symbol rate).
Channels are often called “bins”.
Bin 1 starts at zero frequency (0 - 4.3 KHz).
Upstream can use bins 6 to 38 (~25 - 163 KHz).
Downstream can use bins 33 to 255 (~142 KHz to 1.1MHz). Bins 16 (69 KHz) and 64 (276 KHz) are used for pilot tones.
Symbol loading will vary across bins, to a maximum of 16 bits per symbol (65,536 symbols). Symbol loading in higher numbered bins is limited by SNR.